The Indonesian name for whitefly is "kutu putih" and it is in the insect family Aleyrodidae.
Whiteflies reduce potato and cabbage plant vigour by sucking sap from leaves. There are several species, but all adults are small at about 1.5mm long with white wings.
Adults lay eggs on the underside of young leaves. The eggs are pale when first laid and turn black just before hatching into nymphs.
Whitefly immature stages are called nymphs which occur on the undersides of leaves. They are grey to white, circular and soft-bodied, similar to aphid nymphs. But unlike aphids, whitefly nymphs lack cornicles on the abdomen and do not move once they start feeding.
Symptoms of whitefly damage include wilting leaves and the presence of black sooty mould. These symptoms are rarely seen because only large numbers of whitefly will cause such effects. The sooty mould is a fungus that grows on the sugary honeydew that nymphs and adult whitefly excrete when they are feeding.
When mature, whitefly nymphs form into white oval cocoons on the underside of leaves. Cocoons are cream when not parasitised, yellow when parasitised.
Cocoons from which whitefly adults emerge are grey shells with a split line, and cocoons from which wasp parasites have emerged have a circular hole cut in them.
A video on whitefly stages is available.
Whitefly may be present on weeds so keep the area around crops free of weeds.
Check crops for whitefly during weekly pest monitoring.
Whitefly will cause damage only when present in high numbers.
Several species of whitefly can be pests in potato and cabbage crops. Some of these have a reputation for developing resistance to insecticides so careful consideration is required as to whether infestations require insecticide use and whether natural enemies may control an infestation.
If insecticides are used, delay or avoid insecticide resistance by alternating insecticides with different modes of action.
Natural enemies of whitefly include wasp parasitoids, and predators such as lacewing larvae, ladybird beetles, hover flies, mites and spiders.
If whitefly numbers are high enough to cause crop wilting, insecticides should be applied. A range of contact, systemic and growth regulator insecticides will control whitefly and more than one application may be required to control heavy infestations.
Funding for this work to support Indonesian potato farmers and WA seed potato exports was provided by ACIAR (the Australian Centre for International Agricultural Research) and the Department of Agriculture and Food, Western Australia.